insert into string python

def insert (source_str, insert_str, pos):
    return source_str[:pos]+insert_str+source_str[pos:]

>>> shepherd = "Martha"
>>> age = 34
>>> # Note f before first quote of string
>>> stuff_in_string = f"Shepherd {shepherd} is {age} years old."
>>> print(stuff_in_string)
Shepherd Martha is 34 years old.

>>> line = 'Kong Panda'
>>> index = line.find('Panda')
>>> output_line = line[:index] + 'Fu ' + line[index:]
>>> output_line
'Kong Fu Panda'

var str = "ello";
var letter = "h";
str = letter + str;